The escalating demands for high density and performance associated with non-volatile memory devices require small design features, high reliability and increased manufacturing throughput. The reduction of design features, however, challenges the limitations of conventional methodology.
One type of conventional electrically erasable programmable read only memory (EEPROM) device includes a silicon substrate with an oxide-nitride-oxide (ONO) stack formed on the substrate. A silicon control gate is formed over the ONO stack. This type of memory device is often referred to as a SONOS (silicon-oxide-nitride-oxide-silicon) type memory device. In a SONOS device, the nitride layer acts as the charge storage layer.
The SONOS type memory device may be programmed by a hot electron injection process that injects electrons into the nitride layer where they become trapped. The nitride layer may then store this negative charge.
The SONOS type memory device is typically erased using a hot hole injection (HHI) process. In some SONOS type memory devices, the oxide layer on the nitride layer may be augmented or replaced with a high K material, such as Al2O3. The addition of the high K material permits the SONOS memory device to be erased using mechanisms other than HHI. For example, Fowler-Nordheim (FN) erase mechanisms may be used.
One type of high K material that is used to supplement the ONO stack is alumina. For example, an aluminum oxide may be deposited on top of the top oxide layer to create an Al2O3-oxide-nitride-oxide (AONO) stack. In such a memory device, FN erase mechanisms can be used to erase the memory device. Accordingly, it would be desirable to be able to effectively form memory devices including a high-K layer, such as a memory device with an AONO stack.